Conventionally, an electrostatic chuck to hold a work such as a semiconductor wafer comprises a mount plate on which the work is to be mounted and a support supporting the mount plate. Among electrostatic chucks, there are ones which comprise a heater to heat a work and a heat-uniformizing plate to uniformize heat from the heater that are placed between the base material forming the support and the mount plate. For both the adhesion of the heater and the heat-uniformizing plate and the adhesion of the heat-uniformizing plate and the mount plate, a heat conductive adhesive bond is used. For the adhesion of the heater and the base material, a heat insulating adhesive bond is used. At the outer edge of the mount plate support, there is provided an adhesive bond protecting layer to protect the adhesive layers between the base material and the mount plate sideways.
The degradation of this adhesive bond protecting layer is promoted because of the influence of stress due to the difference in linear expansion coefficient between the mount plate (generally ceramic) and the heat-uniformizing plate (generally aluminum) and erosion by plasma. If the degradation reaches to the adhesive bond layers where heat conductive gas (such as helium) lines or thermo-sensor lines exist, the helium leakage or the vacuum leakage will likely occur, and thus there is the problem that the life time of the electrostatic chuck becomes shorter.